Hydrolix MCP Server

An MCP server for Hydrolix.

Tools

run_select_query
- Execute SQL queries on your Hydrolix cluster.
- Input: sql (string): The SQL query to execute.
- All Hydrolix queries are run with readonly = 1 to ensure they are safe.
list_databases
- List all databases on your Hydrolix cluster.
list_tables
- List all tables in a database.
- Input: database (string): The name of the database.

Effective Usage

Due to the wide variety in LLM architectures, not all models will proactively use the tools above, and few will use them effectively without guidance, even with the carefully-constructed tool descriptions provided to the model. To get the best results out of your model while using the Hydrolix MCP server, we recommend the following:

Refer to your Hydrolix database by name and request tool usage in your prompts (e.g., "Using MCP tools to access my Hydrolix database, please ...")
- This encourages the model to use the MCP tools available and minimizes hallucinations.
Include time ranges in your prompts (e.g., "Between December 5 2023 and January 18 2024, ...") and specifically request that the output be ordered by timestamp.
- This prompts the model to write more efficient queries that take advantage of primary key optimizations

Health Check Endpoint

When running with HTTP or SSE transport, a health check endpoint is available at /health. This endpoint:

Returns 200 OK with the Hydrolix query-head's Clickhouse version if the server is healthy and can connect to Hydrolix
Returns 503 Service Unavailable if the server cannot connect to the Hydrolix query-head

Example:

curl http://localhost:8000/health
# Response: OK - Connected to Hydrolix compatible with ClickHouse 24.3.1

Configuration

The Hydrolix MCP server is configured using a standard MCP server entry. Consult your client's documentation for specific instructions on where to find or declare MCP servers. An example setup using Claude Desktop is documented below.

The recommended way to launch the Hydrolix MCP server is via the uv project manager, which will manage installing all other dependencies in an isolated environment.

MCP Server definition (JSON):

{
  "command": "uv",
  "args": [
    "run",
    "--with",
    "mcp-hydrolix",
    "--python",
    "3.13",
    "mcp-hydrolix"
  ],
  "env": {
    "HYDROLIX_HOST": "<hydrolix-host>",
    "HYDROLIX_USER": "<hydrolix-user>",
    "HYDROLIX_PASSWORD": "<hydrolix-password>"
  }
}

MCP Server definition (YAML):

command: uv
args:
- run
- --with
- mcp-hydrolix
- --python
- "3.13"
- mcp-hydrolix
env:
  HYDROLIX_HOST: <hydrolix-host>
  HYDROLIX_USER: <hydrolix-user>
  HYDROLIX_PASSWORD: <hydrolix-password>

Configuration Example (Claude Desktop)

Open the Claude Desktop configuration file located at:
- On macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
- On Windows: %APPDATA%/Claude/claude_desktop_config.json
Add a mcp-hydrolix server entry to the mcpServers config block:

{
  "mcpServers": {
    "mcp-hydrolix": {
      "command": "uv",
      "args": [
        "run",
        "--with",
        "mcp-hydrolix",
        "--python",
        "3.13",
        "mcp-hydrolix"
      ],
      "env": {
        "HYDROLIX_HOST": "<hydrolix-host>",
        "HYDROLIX_USER": "<hydrolix-user>",
        "HYDROLIX_PASSWORD": "<hydrolix-password>"
      }
    }
  }
}

Update the environment variable definitions to point to your Hydrolix cluster.
(Recommended) Locate the command entry for uv and replace it with the absolute path to the uv executable. This ensures that the correct version of uv is used when starting the server. You can find this path using which uv or where.exe uv.
Restart Claude Desktop to apply the changes. If you are using Windows, ensure Claude is stopped completely by closing the client using the system tray icon.

Environment Variables

The following variables are used to configure the Hydrolix connection. These variables may be provided via the MCP config block (as shown above), a .env file, or traditional environment variables.

Required Variables

HYDROLIX_HOST: The hostname of your Hydrolix server
HYDROLIX_USER: The username for authentication
HYDROLIX_PASSWORD: The password for authentication

Optional Variables

HYDROLIX_PORT: The port number of your Hydrolix server
- Default: 8088
- Usually doesn't need to be set unless using a non-standard port
HYDROLIX_VERIFY: Enable/disable SSL certificate verification
- Default: "true"
- Set to "false" to disable certificate verification (not recommended for production)
HYDROLIX_DATABASE: Default database to use *Default: None (uses server default)
- Set this to automatically connect to a specific database
HYDROLIX_MCP_SERVER_TRANSPORT: Sets the transport method for the MCP server.
- Default: "stdio"
- Valid options: "stdio", "http", "sse". This is useful for local development with tools like MCP Inspector.
HYDROLIX_MCP_BIND_HOST: Host to bind the MCP server to when using HTTP or SSE transport
- Default: "127.0.0.1"
- Set to "0.0.0.0" to bind to all network interfaces (useful for Docker or remote access)
- Only used when transport is "http" or "sse"
HYDROLIX_MCP_BIND_PORT: Port to bind the MCP server to when using HTTP or SSE transport
- Default: "8000"
- Only used when transport is "http" or "sse"

For MCP Inspector or remote access with HTTP transport:

HYDROLIX_HOST=localhost
HYDROLIX_USER=default
HYDROLIX_PASSWORD=myPassword
HYDROLIX_MCP_SERVER_TRANSPORT=http
HYDROLIX_MCP_BIND_HOST=0.0.0.0  # Bind to all interfaces
HYDROLIX_MCP_BIND_PORT=4200  # Custom port (default: 8000)

When using HTTP transport, the server will run on the configured port (default 8000). For example, with the above configuration:

MCP endpoint: http://localhost:4200/mcp
Health check: http://localhost:4200/health

Note: The bind host and port settings are only used when transport is set to "http" or "sse".